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... energy storage (CES) uses liquid air or liquid nitrogen as energy storage media, hence also known as Liquid Air Energy Storage. The basic working principle of the CES is shown in Fig. 1, which includes air liquefaction and power recovery processes. In the air liquefaction process, the ambient air is firstly purified to remove CO 2 and water; then, it is compressed to a high pressure by consuming offpeak electricity or renewable energy, and meanwhile the heat of compression is stored in the heat storage tank for later ...
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... heat of compression from the heat storage tank and finally expands in air turbines to generate peak and stable electricity. Round trip efficiency is usually used to assess the thermodynamic performance of the CES, which is defined as the ratio of power generation during power recovery to power consumption during air liquefaction. It is clear from Fig. 1 that the CES is closely integrated with thermal energy ...
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... energy storage (CES) is closely integrated with Thermal Energy Storage (TES), as shown in Fig. 1. The development of the TES benefits the CES. TES covers a range of technologies based on exploiting different fundamental scientific principles. It can be classified into three groups: sensible heat storage, latent heat storage and thermochemical heat storage. Comparisons of the three groups are shown in Fig. 3. Sensible heat storage ...
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Citations
... Since their significant contribution to improving renewable energy systems and grid load transfer has been recognized in recent years, large-scale energy storage technologies have earned increasing attention (Mitali, Dhinakaran, and Mohamad 2022). One of the most efficient methods that can be used for the storage of large amounts of energy is compressed air energy storage (Navarro et al. 2019). Liquid air energy storage system (LAES) has attracted the attention and research efforts of numerous scholars across the country and abroad to solve the problems of compressed air energy storage resulting from large air chamber volumes and high costs, as well as to reduce the storage volume of the storage medium and to improve the energy storage density (Qi et al. 2022). ...
Liquid air energy storage (LAES), as a promising grid-scale energy storage technology, can smooth the intermittency of renewable generation and shift the peak load of grids. In the LAES, liquid air is employed to generate power through expansion; meanwhile cold energy released during liquid air evaporation is recovered, stored and later utilized for air liquefaction enhancement. However, it is challenging for effective cold recovery from liquid air in the evaporator and cold utilization to compressed air in the cold box. The current cold recovery fluids are exergy-inefficient, and thus the most suitable cold recovery fluids should be determined. In this paper, a practically dynamic LAES system with cold/heat storage packed beds is studied from the startup to stability. Some common cold recovery fluids, such as air, propane, and methanol/propane, are investigated and compared in terms of heat transfer characteristics in the heat exchangers (i.e., evaporator and cold box) and cold storage packed bed. Simulation results show that using pressurized air (10 MPa) as cold recovery fluid results in high heat transfer coefficients in the heat exchangers and cold storage packed bed. Compared to other fluids, the pressurized air leads to a larger exergy efficiency of 78.2% in the cold box, and a comparable exergy efficiency of 89.6% in the evaporator. It is found that pressurized air and methanol/propane are both good cold recovery fluids in view of the heat transfer performance in the cold box and evaporator, achieving similar idealistic round trip efficiency of 53%. However, the consideration of exergy destruction in packed beds will decline the round trip efficiency to 43% for pressurized air and 38% for methanol/propane. The cold storage packed beds with methanol/propane as cold recovery fluids are easier to be penetrated by thermoclines at the same size of pebbles, which causes a lower round trip efficiency. This study gives new insights into the effective cold recovery, storage and utilization process of LAES for industrial applications.
This work presents a steady-state model of a generic liquid air power plant integrated with parabolic trough solar collectors, explores the plant design space, and maximizes its energy and exergy performance. The model is verified against the round trip efficiency of various plant configurations reported in the literature, and the design space exploration entails quantifying the effects of plant mass flow rates, operating pressures, and heat exchanger inventory allocation on the global performance. The multi-objective optimization consists of maximizing both the round-trip and exergy efficiency and identifying their trade-offs via the Pareto front. Results demonstrate the presence of a critical liquid air mass flow rate beyond which reverse cooling is instigated and the plant energy performance is degraded. Furthermore, the two objective functions in the optimization are shown to compete against each other, although the round trip efficiency is deemed as a more practical performance metric while the maximum exergy efficiency design better exploits solar energy as a high- grade heat source. The best design for the plant layout under analysis yields the round trip and exergy efficiency of 20% and 59%, respectively, with the critical mass flow rate of 0.8 kg/s.
Emerging integrated solar thermal conversion and latent heat storage has a great potential in harvesting solar energy continuously and efficiently by avoiding redundant energy transfer processes. However, the energy harvesting performance is limited by weak solar absorption and low thermal conductivity of phase change materials (PCMs). Here, loofah-derived eco-friendly SiC ceramics is proposed for fast, efficient, and compact solar thermal energy storage beyond state-of-the-art. We design a facile way to fabricate eco-friendly porous SiC ceramics with robust structure and tunable porosity by impregnating flour paste into loofah followed by carbonization and molten silicon reaction processes. After impregnation with NaCl-NaF eutectics, broadband sunlight capture with average solar absorptance of 95.25%, rapid thermal transport with thermal conductivity of 20.7 W/mK, and compact latent heat storage with energy storage density of up to 424 kJ/kg are demonstrated simultaneously. Highly conductive light SiC materials, hierarchical continuous loofah skeleton structure, and high energy density eutectics are attributed to this superior performance. This work opens new routes for efficient harvesting solar thermal energy based on biomimetic eco-friendly ceramics.
Liquid Air Energy Storage (LAES) uses off-peak and/or renewable electricity to produce liquid air (charging). When needed, the liquid air expands in an expander to generate electricity (discharging). The produced liquid air can be transported from renewable energy rich areas to end-use sites using existing road, rail and shipping infrastructures. The discharging process occurs at the end-use sites in this case and is therefore decoupled from the charging process (denoted as decoupled LAES). One of key challenges associated with the decoupled LAES is the recovery of cryogenic energy released by liquid air during the discharging process. Here we propose a cryogenic thermoelectric generation (Cryo-TEG) method to effectively recover the cryogenic energy. Both thermodynamic and economic analyses are carried out on the Cryo-TEG. The results are compared with conventional cryogenic Rankine cycles (Cryo-RC). Additionally, system performance of the decoupled LAES integrated with the Cryo-TEG is also evaluated for combined power and cooling supply. The results show that the Cryo-TEG has a thermal efficiency of ∼ 9%, which is much lower than the Cryo-RC (∼39.5%). However, the Cryo-TEG gives a much better economic performance especially as the cooling capacity of liquid nitrogen is below 8.6 MW: the levelized cost of electricity of the Cryo-TEG could be as low as 0.0218 $/kWh, ∼4 times cheaper than that of the Cryo-RC. This demonstrates that the Cryo-TEG is more favourable for cryogenic energy recovery in the small-scale decoupled LAES. With the Cryo-TEG, the decoupled LAES system could achieve an electrical round trip efficiency of ∼ 29% and a combined cooling and power efficiency of ∼ 50%.
Liquid air energy storage (LAES) is increasingly popular for peak-load shifting of power grids, which includes air liquefaction at off-peak hours and power generation at peak hours. The standalone LAES system does not rely on external cold and heat sources, and hence is more favorable for applications. In the standalone LAES system, heat storage in the air liquefaction process and cold storage in the power generation process play a key role on the system performance. The previous studies often chose propane/methanol as cold storage materials, and thermal oils as heat storage materials, which show a relatively higher system performance. However, propane, methanol and thermal oils are flammable, have a high capital cost and require strict safety measures, which are unfavorable for some industrial applications. To address this issue, we propose a novel standalone LAES system with pebbles/rocks as both cold and heat storage materials in packed beds. Such stores have a low capital cost and a high chemical stability and have not been studied in detail before. The dynamic effect of packed beds on the proposed LAES system is investigated from start-up to stable operation for the first time. Our simulation results show that it takes ~10 days for the system to reach a stable operation from start-up mainly due to the cold accumulation in the packed bed, and the average liquid air yield increases from 0.23 at the start-up to 0.56 in the stable operation. Besides, the proposed LAES system gives a round trip efficiency of ~42.8% and a combined heat and power efficiency of ~82.1%. These findings provide valuable information for industrial applications of the LAES technology.
Detailed here is the proposed design of the tertiary side of a Thermal Energy Storage (TES) System to be interfaced with the steam cycle of a Light Water Reactor (LWR) plant. This study extends the understanding provided by many previous investigations (i.e., beyond thermodynamic considerations) by specifically addressing real world constraints associated with the backfit of such a system to an operating LWR. These constraints relate to the feasibility of design modifications during an extended refueling outage, and to licensing, operational, and maintenance considerations. The Korean designed and built APR1400 plant is selected for integration with the TES tertiary system, resulting in a design which can be readily be adapted to most LWR plant. Heat transfer and transport from and to the nuclear steam cycle is by synthetic oil with high temperature capabilities. Heat storage is in the form of packed beds consisting of crushed rock. While the rates of storage and recovery are constrained by the design of the nuclear reactor and steam plant (i.e., 20% of reactor thermal power during storage, and ~11% during recovery) the total stored energy component of the system can be readily and economically scaled to any desired capacity (at the marginal cost of carbon steel vessels filled with rock). Finally, it is proposed that any nuclear installation with water access could employ bulk thermal energy storage built into an Ultra Large Barge for turnkey delivery with a concomitant reduction in installed cost and risk.
Liquid Air Energy Storage (LAES) is one of the most promising energy storage technologies for achieving low carbon emissions. Our research shows that the LAES produces a considerable amount of excess heat that cannot be cost-effectively utilised in a standalone LAES system. On the other hand, the regasification of liquefied natural gas (LNG) often leads to waste of a large amount of high-grade cold energy. Therefore, this paper proposes the integration of the LAES with the LNG regasification process via a Brayton cycle (denoted as LAES-Brayton-LNG), where pressurized propane is used as both the heat transfer fluid and storage material for the LNG cold energy. The excess heat from the LAES works as the heat source and the waste cold from the LNG regasification as the cold source for the Brayton cycle. Such an integrated LAES-Brayton-LNG system does not need to change the existing LAES system configuration, and the LNG regasification process is independent of the LAES system, thus allowing operation flexibilities. Our analyses show that the flexibly integrated LAES-Brayton-LNG system achieves a system exergy efficiency of 57% and could improve the system exergy efficiency of the standalone LAES system by 14.4%. What’s more, it has an electrical round trip efficiency of ∼70.6%, which is ∼56.5% higher than that of the standalone LAES system. Hence, the proposed LAES-Brayton-LNG system is comparable with other large scale energy storage technologies in terms of the electrical round trip efficiency.
